Mössbauer Analysis of Iridium in Pt-Ir/SiO₂ Catalysts

Abstract

The state of iridium in highly disperse~9~imetallic Pt-Ir catalysts supported on amorphous silica was studied by Ir M8ssbauer spectroscopy, after deposition via ion exchange, as well as after calcination, reduction in hydrogen, and on exposure to carbon monoxide.Cyracteristic patterns and relative contributions of adsorbed [Ir(NH 3 ) 5 C1] complexes, IrCl 3 , IrO2 and Pt-Ir alloy particles have been identified.The composition of bimetallic particles indicates a strong tendency for segregation of Pt and Ir.